Buggy code:
public class PreferencesPage extends FieldEditorPreferencePage implements IWorkbenchPreferencePage { private BooleanFieldEditor makeBackup ; public PreferencesPage ( ) { } @ Override public void init ( IWorkbench workbench ) { } @ Override protected void createFieldEditors ( ) { final Composite parent = getFieldEditorParent ( ) ; WorkspaceFileFieldEditor rules = new WorkspaceFileFieldEditor ( Activator . PREF_RULES_FILE , "Validation<seq2seq4repair_space>Rules:<seq2seq4repair_space>" , new String [ ] { "def" } , parent ) ; rules . getTextControl ( parent ) . setToolTipText ( "The<seq2seq4repair_space>file<seq2seq4repair_space>that<seq2seq4repair_space>defines<seq2seq4repair_space>the<seq2seq4repair_space>rules<seq2seq4repair_space>for<seq2seq4repair_space>validation<seq2seq4repair_space>of<seq2seq4repair_space>properties<seq2seq4repair_space>(read-only,<seq2seq4repair_space>write,<seq2seq4repair_space>read//write)" ) ; addField ( rules ) ; BooleanFieldEditor askForBackup = new BooleanFieldEditor ( Activator . PREF_SHOW_BACKUP_DIALOG , "Ask<seq2seq4repair_space>to<seq2seq4repair_space>do<seq2seq4repair_space>backup<seq2seq4repair_space>before<seq2seq4repair_space>applying<seq2seq4repair_space>quick<seq2seq4repair_space>fix?" , parent ) { private Button button ; @ Override protected Button getChangeControl ( Composite parent ) { if ( ( button ) == null ) { button = super . getChangeControl ( parent ) ; button . addSelectionListener ( new SelectionListener ( ) { @ Override public void widgetSelected ( SelectionEvent e ) { makeBackup . setEnabled ( ( ! ( getBooleanValue ( ) ) ) , parent ) ; } @ Override public void widgetDefaultSelected ( SelectionEvent e ) { } } ) ; } return button ; } } ; addField ( askForBackup ) ; makeBackup = new BooleanFieldEditor ( Activator . PREF_DO_BACKUP , "Do<seq2seq4repair_space>backup<seq2seq4repair_space>when<seq2seq4repair_space>applying<seq2seq4repair_space>quick<seq2seq4repair_space>fix?" , parent ) ; makeBackup . setEnabled ( ( ! ( Activator . getInstance ( ) . isShowBackupDialog ( ) ) ) , parent ) ; addField ( makeBackup ) ; BooleanFieldEditor showSummary = new BooleanFieldEditor ( Activator . PREF_SHOW_SUMMARY , "Show<seq2seq4repair_space>summary<seq2seq4repair_space>dialog<seq2seq4repair_space>after<seq2seq4repair_space>validation?" , parent ) ; addField ( showSummary ) ; BooleanFieldEditor nestMarkers = new BooleanFieldEditor ( Activator . PREF_NEST_MARKERS , "Nest<seq2seq4repair_space>markers<seq2seq4repair_space>in<seq2seq4repair_space>the<seq2seq4repair_space>Problems<seq2seq4repair_space>View?" , parent ) ; <START_BUG> nestMarkers . getLabelControl ( parent ) . setToolTipText ( "Display<seq2seq4repair_space>sub<seq2seq4repair_space>validation<seq2seq4repair_space>failures<seq2seq4repair_space>(action,<seq2seq4repair_space>script,<seq2seq4repair_space>rule)<seq2seq4repair_space>as<seq2seq4repair_space>children<seq2seq4repair_space>of<seq2seq4repair_space>their<seq2seq4repair_space>parent<seq2seq4repair_space>properties<seq2seq4repair_space>(actions,<seq2seq4repair_space>scripts,<seq2seq4repair_space>rules)" ) ; <END_BUG> addField ( nestMarkers ) ; } }

Fix:
nestMarkers . getDescriptionControl ( parent ) . setToolTipText ( "Display<seq2seq4repair_space>sub<seq2seq4repair_space>validation<seq2seq4repair_space>failures<seq2seq4repair_space>(action,<seq2seq4repair_space>script,<seq2seq4repair_space>rule)<seq2seq4repair_space>as<seq2seq4repair_space>children<seq2seq4repair_space>of<seq2seq4repair_space>their<seq2seq4repair_space>parent<seq2seq4repair_space>properties<seq2seq4repair_space>(actions,<seq2seq4repair_space>scripts,<seq2seq4repair_space>rules)" ) ;